Organic polysulfides containing two to five or even more sulfur atoms per molecule have been found useful for many purposes such as additives for elastomers, antioxidants for lubricating oils, intermediates for the production of organic chemicals, insecticides, germicides and as additives to diesel fuels to improve the octane number and ignition qualities of these fuels. These compounds have also been found useful in the compounding of extreme pressure lubricants and in the acceleration of rubber treating processes.
Such polysulfide compounds can be prepared by reacting mercaptans with elemental sulfur in the presence of a basic catalyst. For example, Biensan et al (U.S. Pat. No. 3,308,166) discloses that polysulfides can be prepared from a mercaptan and sulfur catalyzed by an amine using an alcohol promoter.
A conventional process for producing an organic polysulfide compound such as di-t-butyl trisulfide is to react a mercaptan such as t-butylmercaptan with elemental sulfur in the presence of a basic catalyst. However, the polysulfide thus prepared is generally associated with some unreacted mercaptans and residual H.sub.2 S contributing to unpleasant odor. Additionally, possibly because of the unreacted mercaptans, the product always becomes very unstable, i.e., the product turns cloudy, probably due to degradation of the polysulfide causing precipitation of sulfur. The instability along with the unpleasant odor greatly reduce the desirability and utility of polysulfide products.
It has also been shown that organic polysulfide compounds cause metal corrosion partly due to the presence of polysulfide compounds having four or more sulfur atoms. A small quantity of these polysulfide compounds having four or more sulfur atoms are always present when a polysulfide compound having less than four sulfur atoms is prepared. Therefore, there is need to develop an improved process for producing an organic polysulfide compound.